It is well-known to use physical signals like movement of the whole body, for example by dancing, for electronic conversion into audio-visual signals. For example, U.S. Pat. No. 5,045,687 discloses an optical instrument capable of registering a person's movement in a defined space and converting the registered movement into musical tones and images. Also, measurement of physiological quantities as electromyographic (EMG) signals, galvanic skin response (GSR), electroencephalographic (EEG) signals, skin temperature, blood pressure, and heart rhythm (electrocardiography or ECG) have been used in biofeedback methods, where the subject is presented for a converted output signal indicative of the actual physiological state of the subject. Thereupon, the subject is able to change the output signal, for instance an audio-visual signal, as a response to a change in the physiological state. U.S. Pat. No. 5,662,117 discloses such a method and apparatus wherein the method is used to teach a person to relax even in a stressful situation. German Pat. No. DE 197 45 508 discloses a method and system where bio-electrical signals are converted to audio-visual signals presented for two  persons that are competing in attaining the most relaxed state. U.S. Pat. No. 6,001,065 discloses a method and apparatus, where bio-electrical signals from a subject as a person, an animal, or a plant are used to control and interact with electronic media such as motion pictures, video games, virtual environments or security systems.
Though the prior art teaches measurements of physiological signals and conversion of these signals into an audio-visual signal, none of these references describes the use of physiological signals as a substitute for lingual communication between people. However, such a system would be a desirable tool for handicapped people who are unable to speak or to form words from letters as well as others who prefer non-verbal communication.